A large high pressure system parked over the Mississippi River Valley, bringing several days of hot, southerly flow across the region. From the afternoon of June 28 to the evening of June 29, the combination of heat and humidity, boosted by recent rain, created dangerous conditions.
Every event with a place to put it; 11 filed by county or forecast zone are drawn at its center, in a lighter ring. Tap one for its entry below.
Deaths and injuries are direct and indirect together, as the offices filed them. Damage is property and crops in the dollars of the year, not adjusted for inflation, and only where an office estimated it.
The episode as NWS FSD wrote it up.
A large high pressure system parked over the Mississippi River Valley, bringing several days of hot, southerly flow across the region. From the afternoon of June 28 to the evening of June 29, the combination of heat and humidity, boosted by recent rain, created dangerous conditions. Some heat index values exceeded 105 to 110 degrees in and near northwest Iowa.
The local office's own words before the first event, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.
NWS Sioux Falls, SD wrote its last area forecast discussion before the first event at Jun 29, 5:28 AM CST, 6 hours 2 minutes earlier.
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</html>Hazardous Weather Outlook National Weather Service Sioux Falls SD 435 AM CDT Mon Jun 29 2026 IAZ001>003-012>014-020>022-031-032-MNZ071-072-080-081-089-090-097- 098-NEZ013-014-SDZ040-056-062-066-067-069>071-300945- Lyon-Osceola-Dickinson-Sioux-O'Brien-Clay-Plymouth-Cherokee- Buena Vista-Woodbury-Ida-Lincoln-Murray-Cottonwood-Nobles-Jackson- Pipestone-Rock-Dixon-Dakota-Brookings-Moody-Minnehaha-Turner-Yankton- Union- 435 AM CDT Mon Jun 29 2026 This Hazardous Weather Outlook is for northwest Iowa, west central Iowa, southwest Minnesota, northeast Nebraska, east central South Dakota and southeast South Dakota. .DAY ONE...Today and tonight. Heat indices will climb into the triple digits this afternoon to early evening, with readings as high as 105 to 108 degrees from around Sioux City toward Spencer and Storm Lake in northwest Iowa. Take precautions to limit your risk of heat illness if spending time outdoors. Scattered strong to severe thunderstorms may develop evening. If storms are able to develop, the main threats with the strongest storms will be hail up to golf ball size and damaging wind gusts up to 75 mph, but a tornado or two and locally heavy rainfall are also possible. There is an additional low risk for an isolated strong to severe storm late tonight into early Tuesday morning. .DAYS TWO THROUGH SEVEN...Tuesday through Sunday. Isolated severe storms are possible again Tuesday night, and perhaps again on Wednesday, but confidence in any details is low at this time. .SPOTTER INFORMATION STATEMENT... Spotter activation may be needed after 5 pm this afternoon. SDZ038-039-050-052>055-057>061-063>065-068-300945- Beadle-Kingsbury-Gregory-Jerauld-Sanborn-Miner-Lake-Brule-Aurora- Davison-Hanson-McCook-Charles Mix-Douglas-Hutchinson-Bon Homme- 435 AM CDT Mon Jun 29 2026 This Hazardous Weather Outlook is for central South Dakota, east central South Dakota, south central South Dakota and southeast South Dakota. .DAY ONE...Today and tonight. Areas of dense fog will reduce visibility to a quarter mile or less early this morning. Conditions are expected to improve after sunrise. There is a low probability that severe storms in central South Dakota could move into areas from Chamberlain to Huron after daybreak. These storms would bring a risk of damaging winds in excess of 70 mph and large hail up to 2 inch diameter if they maintain their current strength. Heat index values will climb into the 90s this afternoon, mainly east of Highway 281. at times Monday afternoon into the evening. Take precautions to limit your risk of heat illness if spending time outdoors. .DAYS TWO THROUGH SEVEN...Tuesday through Sunday. Isolated severe storms are possible again Tuesday night, and perhaps again on Wednesday, but confidence in any details is low at this time. .SPOTTER INFORMATION STATEMENT... Spotter activation may be needed before 9 AM this morning, mainly for areas from around Chamberlain to Huron.
The national radar mosaic for the moment the first event began.
7 excessive heat, 4 heat. Local standard time, as filed.
Dangerous heat index readings reached a brief afternoon peak as high as 108 degrees at Milford, 107 degrees at Terril, and 106 degrees near Lake Park.
Dangerous heat index readings reached a brief afternoon peak as high as 105 degrees at Spencer, 103 degrees 5 miles southeast of Spencer, and 101 degrees at Webb.
Dangerous heat index readings reached afternoon peaks as high as 112 degrees at Sioux Center, 108 degrees near Orange City, 107 degrees at Hull, and 105 degrees near Maurice.
Dangerous heat index readings reached afternoon peaks as high as 110 degrees in Sioux City, 109 degrees at Moville, and 108 degrees in Sergeant Bluff.
Dangerous heat index readings reached afternoon peaks as high as 109 degrees at Ida Grove.
Dangerous heat index readings reached afternoon peaks as high as 114 degrees near Sutherland, 113 degrees near Hartley, and 108 degrees at Sheldon.
Dangerous heat index readings reached a brief afternoon peak as high as 102 degrees near Truesdale and 100 degrees 3 miles south-southwest of Storm Lake.
Dangerous heat index readings reached afternoon peaks as high as 114 degrees 6 miles west of Kingsley, 111 degrees 10 miles east of Akron and at Sioux Center, and 108 degrees 3 miles south-southeast of Westfield.
Dangerous heat index readings reached a brief afternoon peak as high as 103 degrees near Sibley and 102 degrees at May City.
Dangerous heat index readings reached afternoon peaks as high as 113 degrees 5 miles south-southwest of Ellsworth, 112 degrees 4 miles southwest of George, and 109 degrees at Larchwood.
Dangerous heat index readings reached afternoon peaks as high as 110 degrees near Marcus, 107 degrees at Cleghorn, and 105 degrees at Cherokee.
After NWS Directive 10-1605, the rules offices file Storm Data by.
Every storm in Iowa in 2026Every state in 2026This day in weather historyWarnings in Iowa, June 2026
NOAA National Centers for Environmental Information, Storm Events Database, compiled from the National Weather Service’s monthly Storm Data. Complete through 2026-06; NCEI adds each month about 75 days after it ends and revises past years a few times a year. Rebuilt 2026-09-24. Each event’s entry at NCEI: 1351743, 1351804, 1351789, 1351833, 1351835, 1351800, 1351809, 1351828, 1351744, 1351786, 1351827.